But Casillas accepts they face a massive test tomorrow against Valencia.
"We must be careful because they have fast players, rogues who can play good football. They played more defense, but it will be a difficult game we have to win. I believe there is still a chance of winning the league. We play good football, we have worked hard and with some luck we can meet our objectives," he told AS.
"I look at the calendar and they [Barcelona] have three home games with the teams fighting relegation and have two difficult away games at Sevilla and Villarreal and [this weekend] face Espanyol, who if they win, would be safe [from relegation].
"All their opponents have a lot to play for, but ours as well. Valencia sits in third place, Zaragoza are struggling to survive... Barca has the most difficult schedule because their opponents are playing something. When you least expect it there may be surprise."